Accessibility and strength of H-acceptor hydroxyls of ordered mesoporous silicas probed by pyridine donor
| Autor: | Luis Carlos Cides da Silva, José A. Dias, Pablo Teles Aragão Campos, Sílvia C.L. Dias, Alceu T. Silveira, Mateus F. Paiva, Mayara Resende Alves, Márcia Carvalho de Abreu Fantini, Gesley Alex Veloso Martins, Elon F. de Freitas, Maria Clara Hortencio Clemente |
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| Rok vydání: | 2020 |
| Předmět: |
Isothermal microcalorimetry
Chemistry Mechanical Engineering 02 engineering and technology Mesoporous silica 010402 general chemistry 021001 nanoscience & nanotechnology SILICATOS 01 natural sciences 0104 chemical sciences Thermogravimetry Silanol chemistry.chemical_compound Adsorption Mechanics of Materials Polymer chemistry Pyridine General Materials Science Reactivity (chemistry) 0210 nano-technology Mesoporous material |
| Zdroj: | Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual) Universidade de São Paulo (USP) instacron:USP |
| ISSN: | 1573-4854 1380-2224 |
| Popis: | Ordered mesoporous silica (OMS) is an important and useful material for a variety of applications, including catalysis, adsorption, sensing and controlled drug delivery. The surface chemistry and the silanol groups on OMS pores are key properties for the potential modification and application of this material. This research aimed to synthesize (using standard protocols) and differentiate the accessibility and strength of the H-acceptor Si–OH from FDU-12, SBA-16, MCM-41 and SBA-15 by pyridine (Py) donor, where the first two have cubic pore structures and the last two have hexagonal pore structures. Donor–acceptor properties were assessed by calculation of the surface Si–OH densities by thermogravimetry (TG), H2O-TPD/MS, and 29Si MAS and CP/MAS NMR. The nature of the Si–OH groups on these materials was determined to be hydrogen-bonding sites using FT-IR spectroscopy of Py adsorption. The reactivity of these silanol groups was probed by Py-TG and slurry microcalorimetry of Py adsorption in cyclohexane. Differences in accessibility and reactivity were discussed considering the total potential sites on the surface (nOH) versus the actual sites that can react with the Py molecule (nPy). By using microcalorimetry, it was possible to quantitatively distinguish the strength of the sites: The acidity order was approximately the same as the relative amount of silanol groups (Si–OH) and Py on the surface of the OMS materials (αPy): FDU-12 > MCM-41 ≥ SBA-16 > SBA-15. |
| Databáze: | OpenAIRE |
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